Crossover tree system

ABSTRACT

A subterranean oil or gas well apparatus is provided. The apparatus includes a single-bore production tubing hanger arranged concentric with a wellhead. The tubing hanger includes a plurality of ports and channels arranged about the tubing hanger to give operators access to the production tubing annulus and provide chemical injection capability. The ports are closable by a sliding valve. The apparatus also includes annulus and production radial-bore stab assemblies between a christmas tree and an internal crossover assembly. The stab assemblies are extendable and retractable between the chirstmas tree and the crossover assembly to allow the retrieval and installation of each independently.

[0001] This application claims priority of U.S. Provisional ApplicationNo. 60/178,845, filed Jan. 27, 2000, the specification of which ishereby incorporated by reference.

FIELD OF THE INVENTION

[0002] This invention relates generally to subsea oil and gas productionmethods and apparatus and, more particularly, to a crossover christmastree system.

BACKGROUND OF THE INVENTION

[0003] It is conventional practice to complete a subsea well with amulti bore tubing hanger with tubing suspended below. One bore is aproduction bore of between 5 and 10 inches nominal diameter and theother is a smaller annulus bore of about 2 inches. The tubing hanger andthe associated tubing are run into a subsea wellhead on a runningassembly comprising a tubing hanger running tool and a multi bore riseruntil the tubing hanger is landed and sealed in a wellhead housing. Thewellhead carries a blowout preventor (BOP) stack which is connected to amarine riser through which the tubing hanger is run.

[0004] This configuration, with the bores side-by-side is typicalbecause it is relatively simple to seal off the bores in the tubinghanger. This is done immediately after the tubing hanger has been landedby running and setting at least one plug into each bore through themulti bore riser used to install the tubing hanger using a wirelinetechnique so that the plugs close the bores and secure the well duringthe time the tubing hanger is exposed to the ambient environment.

[0005] Once the plugs are installed, the multi bore riser isdisconnected from the tubing hanger and retrieved to the surface, afterwhich the BOP stack is disconnected from the subsea wellhead andretrieved to the surface with the marine riser. At this point, thetubing hanger is exposed to the ambient environment. The multi boreriser is re-used to run a Christmas tree which is landed and locked intothe subsea wellhead simultaneously establishing connections to thetubing hanger. The Christmas tree is installed using a running assemblycomprising the multi bore riser, a safety package including wirelinecutting valves and an emergency disconnect package which allows theseparation of the surface vessel in the event that it becomes necessaryto disconnect the surface vessel from the wellhead. The multi bore riserleads from the upper end of the emergency disconnect package to thevessel. Wirelines can be deployed through the multi bore riser, thesafety package and the Christmas tree in order to retrieve the plugs inthe production bore and the annulus bore. The Christmas tree valves arethen shut while the safety package and the multi bore riser areretrieved to the surface. The Christmas tree is then capped.

[0006] In deeper water, the viability of such a conventional multi boreriser is open to question both from structural and commercialviewpoints. In addition, there are many applications in which a largerfull bore is desirable. Alternatives to multi bore riser systemsutilizing a single bore have been proposed for running and for operatingwith a christmas tree but, while they can be used for plugging theproduction bore, they suffer from the problem of providing annulusaccess with sufficient flow rate capacities to treat a well—and the lackof annulus flow control.

[0007] Further, in deep water it becomes very difficult to alignside-valve christmas tree ports with the tubing hanger.

[0008] Finally, well drilling and completion operations are veryexpensive and often based on per hour rig charges. It is desirable tocomplete wells with a few downhole trips as possible to reduce rig time.In a conventional tubing hanger and christmas tree assembly, theretrieval of the tubing hanger also requires the retrieval of thechristmas tree. It would be desirable and cost efficient to find asystem that would allow separate retrieval of the christmas tree andtubing hanger.

[0009] The present invention is directed to eliminating, or at leastreducing the effect of, one or more of the issues raised above.

SUMMARY OF THE INVENTION

[0010] The invention is directed to a style of Christmas tree whereinthe tubing hanger is landed in the wellhead, and both the tree and thetubing hanger can be removed independently. This independent ability toretrieve either the tree or the tubing hanger, as required, is achievedthrough the use of a crossover piece in the tree. When installed, thecrossover piece directs the flow of the production fluid to theproduction valves outside the tree, and directs the flow of fluids to orfrom the tubing annulus. When the crossover piece is removed, full-boreaccess through the tree is available, and the tubing hanger, landedbelow the tree can be removed with the tree in place One exemplaryembodiment of the present invention encompasses a subterranean oil orgas well assembly. Such an embodiment includes: a wellhead; a Christmastree coupled to the wellhead; and a tubing hanger landed within thewellhead. A sliding valve is disposed within the tubing hanger toselectively allow fluid communication between a first port in thesliding valve and a first port in the tubing hanger. A crossoverassembly is landed within the tree body, and a crossover stab isdisposed within the crossover assembly and adapted to translate thesliding valve between open and closed positions.

[0011] A subterranean oil or gas well assembly comprising: a wellhead; aChristmas tree coupled to the wellhead; and a single bore tubing hangerlanded within the wellhead. The tubing hanger includes production tubingsuspended from it as should be known in the art. The single bore tubinghanger further includes a plurality of first closable ports whichfacilitate fluid communication to an annulus defined by the productiontubing and an innermost casing.

[0012] These and other features of the present invention are more fullyset forth in the following description of preferred or illustrativeembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The foregoing and other features and aspects of the inventionwill become further apparent upon reading the following detaileddescription and upon reference to the drawings in which

[0014]FIG. 1 depicts a crossover tree design in accordance with oneaspect of the invention.

[0015]FIG. 2 depicts the installation/retrieval of the tubing hanger.

[0016]FIG. 3 depicts the installation/retrieval of the tubing hanger.

[0017]FIG. 4 depicts the tubing hanger in the wellhead and temporarilyabandoned.

[0018]FIG. 5 depicts running the tree with the tree fully assembled.

[0019]FIG. 6 depicts a preparation position for retrieving the tree capand crossover assembly.

[0020]FIG. 7 depicts the installation/retrieval of the crossoverassembly.

[0021]FIG. 8 depicts full bore access through the tree.

[0022]FIG. 9a-9 c depict a view of the alignment mechanism on thecossover assembly.

[0023]FIG. 10 depicts a hydraulic schematic for the crossover treesystem (CTS) in the production mode.

[0024]FIG. 11 depicts a perspective overview of the CTS.

[0025]FIG. 12 depicts a cross sectional view of the CTS in the initialsequence positions.

[0026]FIG. 13 depicts a cross sectional view of the CTS in the retrieveBOP stack/ROV install debris cap sequence.

[0027]FIG. 14 depicts a cross section al view of the CTS in the treerunning sequence.

[0028]FIG. 15a depicts a cross sectional view of the CTS in the extendthe crossover assembly stab into the tubing hanger sequence.

[0029]FIG. 15b depicts a cross sectional view of the CTS in the extendthe crossover assembly stab into the tubing hanger sequence, in a secondposition.

[0030]FIG. 16 depicts a cross sectional view of the CTS in the retrievetubing hanger wireline plug/install crossover wireline plug/retrievetree running tool/ROV install debris cap sequences.

[0031]FIG. 17 depicts a cross sectional view of the CTS in the optionalsequence of locking the empty spool body onto the wellhead with the treerunning tool.

[0032]FIG. 18 depicts a cross sectional view of the CTS in the optionalsequences of locking the BOP stack onto the spool body, running thetubing hanger with a multipurpose running tool, and installing thetubing hanger wireline plug.

[0033]FIG. 19a depicts a cross sectional view of the CTS in the optionalsequence of running the crossover assembly with the multi-purposerunning tool in a first position.

[0034]FIG. 19b depicts a cross sectional view of the CTS in the optionalsequence of extending the crossover assembly stab into the tubing hangerin a second position.

[0035]FIG. 20a depicts a cross sectional view of the CTS in the optionalsequence of extending the crossover assembly stab into the tubing hangerin a first position.

[0036]FIG. 20b depicts a cross sectional view of the CTS in the optionalsequence of extending the crossover assembly stab into the tubing hangerin a second position.

[0037]FIG. 21 a cross sectional view of the CTS in the optionalsequences of retrieving the tubing hanger plug, installing crossoverplugs, retrieving the BOP stack, and ROV installing the debris cap.

[0038]FIG. 22 depicts a combination detail of the side stabs.

[0039]FIG. 23 depicts the tubing hanger shuttle valve detail.

[0040]FIG. 24 depicts the tubing hanger shuttle valve detail in crosssection.

[0041]FIGS. 25a-25 c depict details of the annulus flow paths.

[0042]FIG. 26 depicts a cross-sectional top view of the CTS.

[0043]FIG. 27 depicts a top view of the CTS and retractable stabmechanism.

[0044]FIG. 28 depicts a detail of the bevel gears of the retractablestab mechanism.

[0045]FIG. 29 depicts a perspective view of the apparatus according toFIG. 27.

[0046]FIG. 30 is an alternative embodiment of the christmas tree.

[0047]FIG. 31 depicts a cross sectional view of the CTS with a safetytree.

[0048]FIG. 32 depicts a cross sectional view of the CTS in the crossoverassembly installation sequence.

[0049]FIG. 33 depicts a cross sectional view of theinstallation/retrieval of the tree.

[0050] FIGS. 34-35 depict a detail of the crossover assembly/hangerinterface.

[0051]FIG. 36 depicts a perspective view of the annulus stab mechanism.

[0052] FIGS. 37-38 depict details of the electrical interface betweenthe crossover assembly and the tubing hanger.

[0053]FIG. 39 depicts a multiple use running tool.

[0054] While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0055] Illustrative embodiments of the invention are described below. Inthe interest of clarity, not all features of an actual implementationare described in this specification. It will of course be appreciatedthat in the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, that will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

[0056] Previous attempts to develop a tree with the advantages of acrossover tree have resulted in designs wherein a false or dummy tubinghanger is installed in the tree. U.S. Pat. No. 5,372,199 is one exampleof such a design. Similar designs were offered for sale by NationalOilwell prior to the date of the cited patent. However, such designswere cumbersome and required additional steps to retrieve specificcomponents. The current invention overcomes this and other limitationsof the prior art trees.

[0057] Turning now to the Figures, and in particular FIG. 1, a CrossoverChristmas tree 2 with a tubing hanger 4 installed within a wellhead 6 inaccordance with one embodiment of the invention is disclosed. Theassembly shown in FIG. 1 represents one embodiment of the crossover treesystem and the associated assembly fully installed. Tree 2 is connectedto a wellhead 6 by a tree connector 3. As shown in FIG. 10, treeconnector 3 can be hydraulically actuated such that a lock down ring 58mates with an exterior profile on wellhead 6. Other types of treeconnectors generally known in the art can be adapted to couple the tree2 to the wellhead 6.

[0058] The assembly shown in FIG. 1 includes tubing hanger 4, which isinstalled substantially concentrically within wellhead 6. In oneembodiment, tubing hanger 4 is a concentric tubing hanger, seven inchesin diameter, but may range in size as required for a particular fielddevelopment. Eccentric or dual bore tubing hangers may be used, in otherembodiments not shown. Tubing hanger 4 rests on a shoulder 8 of wellhead6, and the annulus between then tubing hanger 4 and the wellhead 6 issealed. A tubing hanger lock down ring 56 helps secure tubing hanger 4within tree 2. The lower end of tubing hanger 4 suspends a downholetubing 7 (shown schematically in FIG. 10) to facilitate a productionflow from wellbore to surface when the downhole safety valve 9 is open.

[0059] A crossover assembly 10 is disposed within the bore of thecrossover tree 2 such that the assembly bore 11 is substantially coaxialwith the bore 5 in the tubing hanger 4. A crossover stab 12 sealablymates with tubing hanger 4. The annulus between the crossover assembly10 and the tree 2 is sealed, for example by crossover seal 40 disposedbetween the crossover assembly 10 and tree 2.

[0060] In the embodiment shown in FIG. 1, crossover assembly 10 andcrossover stab 12 are installed substantially concentrically with hanger4, with the distal end of crossover stab 12 extending partially throughthe interior of hanger 4. As seen more distinctly in FIGS. 15A and 15B,a plurality of seals 14 seal between hanger 4 and crossover stab 12.Disposed between crossover stab 12 and hanger 4 is a sliding valve 16,which may also be called a shuttle valve. Sliding valve 16 is shown inthe down or operating position in FIG. 1 (the details of sliding valve16 are discussed below). In some embodiments a biasing element, such asa compressed spring, may be disposed in the area labeled 15 in the FIG.1 embodiment to bias the sliding valve 16 to a closed (up) positionwherein ports such as 17 and 17 a (as shown more clearly in FIGS. 15Aand 15B) are misaligned. In the embodiment shown sliding valve 16 isactuated between open and closed position by the application ofhydraulic pressure to space 15.

[0061] Referring to FIGS. 23 and 24, sliding valve 16 may include a body156 with opposing ports or bores 17 and 19. In the embodiment of FIG. 1,bore 17 is an annulus access bore or port. Bore or port 19 is shown inthe embodiment of FIGS. 23 and 24 as a chemical injection bore. Body 156of valve 16 may exhibit flat machined faces 152 and 154 on the outerdiameter of the body at bores 17 and 19. A second annulus port 17 a witha sealing face meets flat machined face 152. Port 17 a is attached to aspacer 164 and is in fluid communication with annulus access bore 18 viaa plurality of holes 166 arranged about the circumference of the spacer.A plurality of seals (not shown) seal between spacer 164 and second port17 a.

[0062] Adjacent to spacer 164 opposite the port 17 a is an adjustableplug 168. A plurality of seals (not shown) on adjustable plug 168inhibits leakage past the plug. Adjustable plug 168, spacer 164, andport 17 a are arranged within a radial bore 170 in tree 2. Adjustableplug 168 may have a hex recess 172 to allow an operator to adjust thecompression between machined face 152 on and the sealing face of port 17a.

[0063] As shown in the figures, valve 16 may include a chemicalinjection bore or port 19. Chemical injection port 19 includes achemical injection adjustable plug 174 adjacent a chemical injectionspacer 176. Chemical injection spacer 176 includes a plurality of holes178 to facilitate fluid communication with a chemical injection bore 23in tubing hanger 4. Chemical injection adjustable plug 174 may include aplurality of seals (not shown) to inhibit leakage past the plug.Chemical injection spacer 176 attaches to chemical injection second port19 a. Chemical injection second port 19 a includes a sealing face whichmeets flat machined surface 154. Chemical injection adjustable plug 174,spacer 176, and second port 19 a are arranged within a second radialbore 178 in tree 2. Chemical injection adjustable plug 174 may have ahex recess (not shown) to allow an operator to adjust the compressionbetween machined face 154 on and the sealing face of second port 162.

[0064] As shown in FIG. 23, shuttle valve 16 is in a first or closedposition. A first plurality of seals 180 inhibit fluid leakage betweenbody 156 and hanger 4. A second plurality of seals 182 may furtherinhibit fluid leakage. The seals may include a primary metal-to-metalseal and secondary elasomer or polymer seal, with retainers in between.In the first position (shown in FIGS. 23 and 24), annulus access bore 17is not aligned with second annulus access port 17 a. Likewise, chemicalinjection bore 19 is not aligned with second chemical injection port 19a. However, in some embodiments, one or both of annulus access bore 17and chemical injection bore 19 is in fact lined up with its associatedsecond port (17 a and 19 a) in the first position.

[0065] Crossover stab 12 includes an annulus access channel 18facilitating fluid communication to a downhole annulus 21 between theproduction tubing 7 and the innermost casing (tubing annulus not shown).Annulus access channel 18 is substantially longitudinal through tubinghanger 4, crossover stab 12, crossover assembly 10, and tree 2. Annulusaccess channel 18 is typical of a plurality of annulus access channels18 shown in cross-section in FIGS. 25a-25 d. In the section shown inFIGS. 25a and 25 b, the first portion of annulus access channels 18 aredesignated 18 a and are arranged interior to the crossover assemblybetween the interior wall 200 and the exterior diameter 202. The numberand size of annular access channels 18 a is a function of the flowcapability desired. Typically the equivalent flow area of thecombination of annulus access channels 18 a is at least 1.5 inches,however this equivalent flow area may vary according to the particularoperation. The equivalent flow area may be determined by operationalstandards to provide sufficient flow to, for example, kill a well withheavy fluids in the event of an emergency. Annulus access channels 18 aconverge to a common eccentric connector 204 which provides for fluidcommunication from each of annulus access channels 18 a to continuethrough another plurality of larger annulus access channels, for examplethe three larger annulus access channels 118 b shown in FIGS. 25a , 25c, and 25 d. FIG. 25c is a view in the upward direction of the sectionshown in FIG. 25a, which is in the opposite direction of same sectionshown in FIG. 25b. Annulus access channels 18 a and 18 b advantageouslyprovide an equivalent flow area to operationally manage the well whilealso allowing for a single bore tubing hanger. Similar channels may bepart of the crossover tree system to provide for chemical injectiondownhole, or to provide communication with downhole equipment such aspressure and temperature sensors. Those skilled in the art willappreciate that the disclosure of the annulus communication system isapplicable to many other types of downhole communication. In theexemplary embodiment shown, chemical channels 23 extend throughcrossover assembly 10 to facilitate chemical injection into productiontubing 7 in much the same way as annulus access channels 18. In theembodiment shown, the plurality of chemical channels 23 provide aminimum equivalent flow area of 0.375 inches to provide adequate flow tothe production bore as necessary. It will be understood by one of skillin the art with the benefit of this disclosure, however, that otherequivalent flow areas deviating substantially in either direction from0.375 inches can be obtained as required for the particular application.

[0066] One or more annulus valves 20 may isolate the sections of annulusaccess channel 18 between the tree 2 and the crossover assembly 10.Annulus valve 20 is shown in FIG. 1 exterior to the tree body, but itmay be located anywhere along annulus access channel 18. A secondannulus valve 21 may also be used as shown in FIGS. 1 and 16. While theannulus valves and piping are shown with flanged connections to the tree2, other types of connections can be substituted, or portions of theannulus piping or valves may be integral to the tree body as shown inFIG. 30.

[0067] Annulus access channel 18 extends through a radial bore 32 intree 2, continues outside the body of tree 2, then re-enters the body oftree 2 and continues substantially longitudinal with the proximal end oftree 2. A retractable radially extending annulus stab assembly 36extends between radial annulus bore 32 in tree 2 and crossover assembly10. The retractability of an annulus stab 35 advantageously allows forindependent installation and retrieval of tubing hanger 4, crossoverassembly 10, and the tree 2. Annulus access channel 18 terminates at aproximal annulus port 34 which facilitates fluid communication betweenthe tubing annulus and the surface. While annulus port 34 is shown abovethe crossover assembly 10, it may be located adjacent or below thecrossover assembly.

[0068] Annulus stab 35 may be operable by hydraulic or electricactuation, or it may be mechanically operated. In the embodiment shown,annulus stab 36 is operated mechanically. The details of the annulusstab assembly 36 are found in FIGS. 26-29. For example, annulus stab 35may be operable by ROV (not shown). The ROV may be a standard remoteoperated vehicle or it may be any other remotely operated vehicle. TheROV provides rotational movement to annulus stab mechanism 210 to extendand/or retract annulus stab 35 between crossover assembly 10 and tree 2.Annulus stab mechanism 210 shown in FIGS. 26-29 includes first andsecond shafts 212 and 214 extending from the annulus stab mechanism.Distal end 216 of second shaft 214 is adapted to connect to an ROV.Proximal end 218 of second shaft 214 is operatively connected to a pairof bevel gears 220 and 222 which are approximately 90 degrees out ofphase with one another. Therefore, rotation of second shaft 214 istranslated 90 degrees to rotate first shaft 212. In an alternativeembodiment, first shaft 212 is rotated directly without the use of asecond shaft or set of gears. First shaft 212 is threadedly connected toannulus stab 35. Annulus stab 35 includes an anti-rotation key 224 whichprevents the annulus stab from rotating with first shaft 212. Therefore,as first shaft 212 rotates, the rotational movement is translated viathe threaded connection with annulus stab 35 into strictly axialmovement of the annulus stab. Upon connection between second shaft 214and the ROV, rotation of the second shaft may ultimately accomplish theextension or retraction of annulus stab 35 into and/or out of engagementwith crossover assembly 10. Alternatively, annulus stab 35 may behydraulically or electrically extended and retracted (not shown). FIG.36 shows in perspective view the annulus stab mechanism 36.

[0069] Crossover stab 12 also includes a downhole safety valve controlassembly 92 which is in communication with a safety valve access channel94 through crossover stab 12. As shown in more detail in FIG. 15A,gallery seals 14 prevent the flow of hydraulic fluid associated withsafety valve access channel 94 substantially above or below the channel.When the sliding valve 16 is in the open or down position as shown inFIG. 15B, channel 94 aligns with a channel in the tubing hanger 4 (notshown) to provide hydraulic communication downhole. When the slidingvalve 16 is in the closed or up position as shown in FIG. 15A, channel94 is not aligned with the channel in the tubing hanger 4 (not shown)and hydraulic communication is not present (putting the downhole safetyvalve into its fail-closed position). As such, downhole safety valvecontrol assembly 94 and safety valve access channel 94 allow theoperator to open or close the downhole safety valve 9 (shown in FIG. 10)as necessary.

[0070] A crossover seal 38 seals the annulus between crossover assembly10 and tree 2 and may serve as a second barrier to any possible leaksacross crossover seal 40 in crossover assembly 10. Seal 38 may becomprise metal-to-metal sealing elements or may comprise resilientsealing elements.

[0071] In the embodiment of FIG. 1, a wireline plug 24 is disposedwithin crossover assembly 10. A second wireline plug 26 is also disposedwithin crossover assembly 10. Wireline plugs 24 and 26 provide a multiseal between the production fluids entering tubing hanger 4, and capassembly 42. Plugs 24 and 26 may comprise mechanical or hydraulic plugs,may be retrievable using wireline, coiled tubing, or pipe, or may bevalves or other closures which are known in the art. In the embodimentsof FIGS. 10 through 21, both closures are installed in crossoverassembly 10.

[0072] At least a portion crossover assembly 10 and tubing hanger 4 arelocated radially interior to tree 2. Crossover assembly 10 hasassociated lock down ring 30 to position the crossover assembly securelywithin tree 2 and to prevent dislocation after the assembly is landedand locked.

[0073] In one embodiment, tree 2 includes a radially extendingproduction stab assembly 44. Production stab assembly 44 includes a treebore 46, which is aligned with a crossover bore 48 in crossover assembly10. A production stab 50 extends between crossover bore 48 and tree bore46 in the position shown in FIG. 1. A plurality of production seals 52seal between the production stab 50 and bores 46 and 48. Production stab50 is retractable as described below. One or more production valves,such as valve 54 shown, may be attached to production stab assembly 44to control the flow of produced hydrocarbons. FIG. 10 shows a generalarrangement including production master valve (PMV) 54 and productionwing valve (PWV) 99. One or more of valves 54 and 99 may be flanged andbolted to the tree 2, as is shown for valve 54 in FIG. 1, or one or moreof the valves may be integral to a valve block or to the tree body asshown in FIG. 30. The embodiment of FIG. 2 shows production valve 54adjacent production stab assembly 44, but it will be understood thatproduction valve 54 may be integral to the production stab assembly asshown in FIG. 30.

[0074] Similar to annulus stab 35, production stab 50 may be operable byhydraulic or electric actuation, or it may be mechanically operated. Inthe embodiment shown, production stab 50 is operated mechanically. Forexample, production stab 50 may be operable by an ROV (not shown). TheROV provides rotational movement to a production stab mechanism 230 toextend and/or retract production stab 50 between crossover assembly 10and tree 2. Production stab mechanism 230 shown in FIGS. 26-29 includesfirst and second shafts 232 and 234 extending from the production stabmechanism. Distal end 236 of second shaft 234 is adapted to connect toan ROV. Proximal end 238 of second shaft 234 is operatively connected toa pair of bevel gears 220 and 222 which are approximately 90 degrees outof phase with one another. Therefore, rotation of second shaft 234 istranslated 90 degrees to rotate first shaft 232. In an alternativeembodiment, first shaft 232 is rotated directly without the use of asecond shaft or set of gears. First shaft 232 is threadedly connected toproduction stab 50. Production stab 50 includes an anti-rotation key 240which prevents the production stab from rotating with first shaft 232.Therefore, as first shaft 232 rotates, the rotational movement istranslated via the threaded connection with production stab 50 intostrictly axial movement of the production stab. Upon connection betweensecond shaft 234 and the ROV, rotation of the second shaft mayultimately accomplish the extension or retraction of production stab 50into and/or out of engagement with crossover assembly 10. Alternatively,production stab 50 may be hydraulically or electrically extended andretracted (not shown). Second shafts 234 and 214 may extend through astandard ROV panel 242, along with an alignment pin shaft 244. FIG. 35shows in perspective view the annulus stab mechanism 36.

[0075] With the assembly as shown in FIG. 1, production fluids may entertubing hanger 4 from the wellbore and continue through a portion ofcrossover assembly 10. The production fluids are then directed throughcrossover bore 48 as wireline plug 26 inhibits further progression upthrough crossover assembly 10. Production fluids continue through treebore 46 and into the radially extending production stab assembly 44.When production valve 54 is open, production fluids then continue into aflow line 246 for further transportation to a desired location. Anoperator also has access, according to the embodiment shown in FIG. 1,to the annulus of the wellbore tubing through annulus access channel 18.The access to the annulus may be important, for example, to allow anoperator to circulate fluids, to relieve pressure in the annulus, or tobullhead the well for example. Should there be any leakage past eitherwireline plug 26 or crossover seal 40, a redundant set of seals onwireline plug 24 and seal 41 prevent further leaking. A perspective viewof the apparatus of FIG. 1 is shown in FIG. 38.

[0076] Referring next to FIGS. 2 and 2b, one of many sequences ofinstallation, retrieval, or workover that are possible in accordancewith the invention is described. FIGS. 2, 2b and 12 depict theinstallation and/or retrieval of tubing hanger 4 within wellhead 6.Generally, tubing hanger 4 is installed while a blowout preventor (BOP)stack 60 is attached to wellhead 6 or to the tree 2. BOP stack 60 isconventional and well known to one of skill in the art with the benefitof this disclosure. Referring to FIG. 3, with BOP stack 60 in place,tubing hanger 4 and crossover stab 12 are inserted into or retrievedfrom wellhead 6. Crossover stab 12 is in the working or down position asshown in FIGS. 1 and 2b. Tubing hanger 4 and crossover stab 12 areattached to a multi purpose running tool 62. Multi purpose running tool62 is also shown in FIG. 39. In FIG. 2, however, the christmas tree 2has also been installed and only the tubing hanger has been installedwithout the crossover stab. In some embodiments tubing hanger 4 includestubing hanger collet fingers 64, which are engaged with a collet 66 atthe distal end of multi purpose running tool 62 during installationand/or retrieval of tubing hanger 4. When tubing hanger 4 is beinginstalled, the hanger continues downhole via multi purpose running tool62 until it engages wellhead shoulder 8. When tubing hanger 4 engageswellhead shoulder 8, tubing hanger lockdown ring 56 locks the hanger inplace and multi purpose running tool 62 may be returned to surface.

[0077] Referring next to FIGS. 3 and 13, with tubing hanger 4 positionedwithin wellbore 6, crossover stab 12 is removed, allowing the slidingvalve 16 to be in the closed or up position. A wireline plug 68 or otherclosure is set inside the tubing hanger through BOP stack 60. The BOPstack is then retrieved and a temporary abandonment/debris cap assembly42 is installed and attached to wellhead 6 in the position shown inFIGS. 3 and 13. Tubing hanger sliding valve 16 is in the up or sealedoff position in this sequence to prevent flow through the annular accessor chemical injection porting, as the assembly awaits the installationof tree 2.

[0078] Referring next to FIG. 5, the temporary abandonment/debris capassembly 42 and wireline plug 68 have been removed and fully assembledtree 2 is installed. Tree 2 is run on tree running tool 70 withcrossover assembly 10, crossover stab 12, and plug 24 in place insidetubing hanger 4. Crossover stab 12 is in the up or running position andtubing hanger sliding valve 16 is in the up or sealed position, whichseals off the tubing annulus communication, as well as other downholecommunication such as the safety valve 9 and injection lines at thesliding valve 16. Tree running tool 70 is attached to the exterior oftree body 2 via tree running tool lock down ring 72. The complete treeassembly 2 is run until tree connector lock down ring 58 engages withwellbore 6 and the tree is secured in the position shown in FIG. 5.

[0079] Referring next to FIG. 6, tree assembly 2 is shown in sequencewherein preparation is made for retrieving crossover assembly 10. Thepreparation for retrieval of crossover assembly 10 comprisesreinstalling BOP stack. In the sequence shown in FIG. 6, BOP stack 60 isbeing run in and lock down ring 74 has not yet engaged tree 2. In FIG.7, BOP 60 is installed and connected to the proximal end of tree 2. BOPlock down rings 74 are engaged with tree 2 at the proximal end of thetree. If any wireline plugs have been set in the crossover assembly theymay be retrieved and wireline plug 68 inside tubing 4 is set, inpreparation for retrieving crossover assembly 10.

[0080] As shown in FIG. 7, the multi purpose running tool 62 may beinserted through BOP stack 60 to retrieve crossover assembly 10. Multipurpose running tool is shown attached to crossover assembly 10. In theembodiment shown in FIG. 7, the attachment between crossover assembly 10and multi purpose running tool 62 is facilitated by an crossoverassembly collet finger 76 engaged with collet 66 of multi purposerunning tool 62. Crossover assembly collet finger 76 may be mounted onan exterior surface of crossover assembly 10 as shown in the Figures.With the multi purpose running tool 62 attached to crossover assembly10, the running tool and tree cap may be either retrieved or installed.When crossover assembly 10 is installed, its operational positionrelative to tree 2 is facilitated by crossover assembly lock down ring28, which is engageable with tree 2 as discussed above. In addition,during installation and retrieval of crossover assembly 10, crossoverstab 12 is in the up or installation/retrieval position as shown.

[0081] The engagement of collet fingers 76 and collet 66 constitute onemechanism of attachment between crossover assembly 10 and running tool62. Other alternative attachment mechanism may be used. Duringinstallation and retrieval of crossover assembly 10, sliding sleeve 16is in the up or installation/retrieval position as shown. In addition,production stab 50 and annulus stab 35 are retracted before installationor retrieval proceeds. The retraction of the production stab 50 andannulus stab 35 is accomplished by a mechanical ROV in the preferredembodiment, but other means for actuation including, but not limited to,hydraulic and/or electric, may be used. [If a hydraulic system is used,production stab 50 and annulus stab 35 may be normally biased to theretracted positions with the extension of each accomplished by hydraulicfluid. Alternatively, production stab 50 and annulus stab 35 may bemotivated to their respective extended and retracted positions withhydraulic pressure without a bias. Hydraulic control lines (not shown)extending to sealed void areas between the stab assembly 44 and theproduction stab 50, or between the annulus stab 35 and the annuluspiping, are one means of such control. In a preferred embodiment, oneset of hydraulic lines will control both sets of stabs. Preferrably,production stab 50 and annulus stab 35 may be actuated by mechanicalmeans such as the production stab mechanism 230. After installation, andafter crossover assembly 10 is positioned in the tree with crossoverbore 48 aligned with tree bore 46, annulus stab 35 and production stab50 are extended to the position shown in FIG. 1.

[0082] Referring next to FIG. 8, the tree assembly is shown withoutcrossover assembly 10. In this configuration, which may be beforeinstallation of crossover assembly 10, or after retrieval of the same,full bore access to the wellbore through tubing hanger 4 is available.Full bore access advantageously enables workover of the well or otherrepairs and maintenance. Tubing hanger sliding valve 16 is in the up orsealed position in full bore access position to seal off access to thetubing annulus (not shown). Wireline plug 68 is also in place withintubing hanger 4 in this configuration. In order to accomplish theinstallation and/or retrieval of the crossover assembly, however, theproduction stab 50 and annulus stab 35 must first be retracted as shown.

[0083] Referring next to FIG. 31, the crossover assembly 10 is beinginstalled through BOP 60.

[0084] Referring next to FIG. 32, crossover assembly 10 has beeninstalled by multi purpose running tool 62 and crossover stab 12extended to force sliding valve 16 into the open position. Wirelineplugs 24 and 26 may then be set in anticipation of production.Alternatively, in a retrieval operation, wireline plugs may be retrievedand crossover assembly 10 and crossover stab 12 may be retrieved aswell.

[0085] Referring next to FIG. 33, an installation/retrieval sequence forchristmas tree 2 is shown. Christmas tree 2 is shown running on a treerunning tool 250. Tree running tool 250 may be used similarly toretrieve tree 2.

[0086] Referring next to FIGS. 34 and 35, a detail of the interfacebetween crossover assembly 10 and tubing hanger 4 is shown. The flowpath of annulus access channels 18 are more clearly seen as it extendsthrough the crossover assembly and to the tubing hanger via an annuluscavity 252. Likewise, the flow path of the chemical injection channels23 are more clearly seen as they extend through the crossover assemblyand to the tubing hanger via a second cavity 254. Sliding valve 16facilitates and/or prevents the flow of through all of the annulusaccess channels 18 and chemical injection channels 23.

[0087] In some embodiments of the present invention the engagementbetween crossover assembly 10 and tubing hanger 4 includes one or moreelectrical contacts 260. As shown in FIGS. 37-38, the electricalcontacts may be separated isolated by a number of seals 262.

[0088] Referring next to FIGS. 9a-9 c, it can be seen that an integralorientation helix 82 may be included on crossover assembly 10.Orientation helix 82 shaped such that upon installation of crossoverassembly 10, the assembly is directed into the correct orientationposition with crossover bore 48 aligned with tree bore 46. Orientationhelixes and their use are well known in the art. Alignment pin 270extending through tree 2 engages helix 82 and directs the crossoverassembly to the desired orientation.

[0089] The present invention thus advantageously facilitates ahorizontal tree and tubing hanger to each be independently retrievablewith full-bore wellhead access.

[0090] Referring next to FIG. 10, a hydraulic schematic for thecrossover tree system (designated CTS in FIGS. 10 through 21) inaccordance with one embodiment of the invention in the production modeis disclosed. The production system valving may include a productionmaster valve 54 and optionally a production wing valve 99 to facilitatecontrol of the production fluids from the wellbore. Access to the tubingannulus may also be facilitated by the valving scheme shown in FIG. 10.An annulus master valve 20 facilitates primary access to the annulus. Anannulus wing valve 21 may allow the flow of annular fluids to anexternal connection or may be the means by which annular fluids areintroduced through an external connection. In series with the annularmaster valve may be an annulus circulation valve 100 to regulate flowand/or pressure in the annulus and provide a communication with thelongitudinal throughbore of tree 2. In addition, a crossover valve 102may allow the operator to open or close fluid communication between theproduction line and the annulus.

[0091] Referring next to FIG. 12, one of a second set of sequences inaccordance with the invention is shown. FIG. 12 depicts the installationand/or retrieval of tubing hanger 4 within wellhead 6. Generally, tubinghanger 4 is installed while a blowout preventor (BOP) stack 60 isattached to wellhead 6. BOP stack 60 is conventional and well known toone of skill in the art. With BOP stack 60 in place, tubing hanger 4 andcrossover stab 12 are inserted into or retrieved from wellhead 6.Crossover stab 12 is in the working or down position as shown in FIGS. 1and 2. Tubing hanger 4 and crossover stab 12 are attached to multipurpose running tool 62. In some embodiments tubing hanger 4 includestubing hanger collet fingers 64, which are engaged with a collet 66 atthe distal end of multi purpose running tool 62 during installationand/or retrieval of tubing hanger 4. When tubing hanger 4 is beinginstalled, the hanger continues downhole via multi purpose running tool62 until it engages wellhead shoulder 8. When tubing hanger 4 engageswellhead shoulder 8, tubing hanger lockdown ring 56 locks the hanger inplace and multi purpose running tool 62 may be returned to surface. In apreferred embodiment, tubing hanger 4 is a non-oriented tubing hanger,although oriented tubing hangers may be provided.

[0092] Referring next to FIG. 13, with tubing hanger 4 positioned withinwellbore 6, crossover stab 12 is removed and a wireline plug 68 or otherclosure is set inside the tubing hanger through BOP stack 60. The BOPstack may be retrieved and a temporary abandonment/debris cap assembly42 may be installed and attached to wellhead 6 in the position shown inFIG. 13. Tubing hanger sliding valve 16 is in the up or sealed offposition in this sequence to prevent flow through the annular access orchemical injection porting, as the assembly awaits the installation oftree 2.

[0093] Referring next to FIG. 14, the temporary abandonment/debris capassembly 42, wireline plug 68 remains in place, and fully assembled tree2 is installed. Tree 2 is run on tree running tool 70 with internal treecap 22, crossover assembly 10, and crossover stab 12 inside tree body 2.Plugs 24 and 26 are not installed inside tree body 2 in this sequence.Crossover stab 12 is in the up or running position and tubing hangersliding valve 16 is in the up or sealed position, which seals off thetubing annulus (not shown) at the valve. Tree running tool 70 isattached to the exterior of tree body 2 via tree running tool lock downring 72. The complete tree assembly 2 is run until tree lock down ring58 engages with wellbore 6 and the tree is secured in the position shownin FIG. 14.

[0094] Referring next to FIGS. 15a and 15 b, a detailed view ofcrossover stab assembly 12 is shown. In FIG. 15a, crossover stab 12 isin the up or running position and tubing hanger sliding valve 16 is inthe up or sealed position, which seals off the tubing annuluscommunication, chemical injection lines, and the downhole safety valvehydraulics as tree 2 is installed.

[0095] For example, FIG. 15a shows that in the up or running position,first ports 17 (the annulus communication ports) in sliding valve 16 donot align with first ports 17 a in tubing hanger 4. It will beunderstood to those of skill in the art that port 17 a in the tubinghanger 4 may be one of several ports radially spaced around the tubinghanger, and extend down through the tubing hanger body to the tubingannulus. First ports 17 a in tubing hanger 4, which may be arrangedabout the inner circumference of the tubing hanger, are preferablyarranged equidistantly around the inner circumference of tubing hanger4. By sizing the ports properly and selecting the appropriate number ofports first ports 17 a provide a fluid communication path withsufficient flow area to the tubing annulus. The number of ports and/orthe size of the ports may vary depending on the use and fieldcharacteristics.

[0096] Similarly, second ports 19 a may provide a fluid communicationpath for chemical injection lines downhole for facilitating chemicalinsertions into the production and/or the formation. It will beappreciated that any number of porting arrangements and communicationsdownhole may be provided.

[0097] The communications paths facilitated by first ports 17 a andsecond ports 19 a are, however, sealed off from respective first andsecond ports 17 and 19 in FIG. 15a. When tree 2 has been set, crossoverstab 12 may be extended into tubing hanger 4 to the position shown inFIG. 15b until first ports 17 and second ports 19 in valve 16 align withfirst ports 17 a and second ports 19 a in tubing hanger 4, respectively.Alignment is accomplished when the shoulder 13 of shuttle valve 16contacts ledge 90 of tubing hanger 4.

[0098]FIG. 16 depicts the next sequence in which the tubing hanger plug68 is retrieved on wireline and crossover wireline plugs 24 and 26 areinstalled as shown. Tree running tool 70 (not shown in FIG. 16) may thenbe retrieved and an ROV may install the temporary abandonment/debris cap42.

[0099] An optional set of sequences are shown in FIGS. 17-21 and aredescribed as follows. Referring to FIG. 1, tree 2 may be run with anempty body on tree running tool 70. In this sequence, the internal treecap, crossover assembly 10, crossover stab 12, and plugs 24 and 26 arenot in place inside tree body 2. Tree 2 is locked onto wellhead 6 asdescribed previously.

[0100] Referring next to FIG. 18, BOP stack 60 is run and locked ontotree 2 via BOP lockdown ring 74 which mates with matching profile 95 ontree 2. Tubing hanger 4 may be run in on multi use running tool 62 asdescribed above. No orientation apparatus is required with the runningof the tubing hanger. A wireline plug 68 may be installed in the tubinghanger (not shown in FIG. 18).

[0101] Referring next to FIGS. 19a and 19 b, crossover assembly 10 maybe run on multi use running tool 62. Crossover assembly 10 self-orientswithin tree 2 with the aid of an orientation helix as described aboveand shown in FIG. 9. As shown in FIG. 19b, which is a detail of themulti use running tool 62, the crossover stab 12 (not shown in FIG. 19b)may be replaced by a bore protector

[0102]FIGS. 20a and 20 b, similar to FIGS. 15a and 15 b, show theextension of crossover stab 12. In FIG. 20a, crossover stab 12 is in theup or running position and tubing hanger sliding valve 16 is in the upor sealed position, which seals off the tubing annulus (not shown) atthe valve as tree 2 is installed. FIG. 20a shows that in the up orrunning position, upper ports 17 and lower ports 19 in sliding valve 16do not align with upper ports 17 a and lower ports 19 a in tubing hanger4. Upper ports 17 a in tubing hanger 4, which may be arranged about theinner circumference of the tubing hanger, are preferably arrangedequidistantly around the inner circumference of tubing hanger 4. Upperports 17 a provide a fluid communication path to the tubing annulus (notshown). Lower ports 19 a provide a fluid communication path to thedownhole tubing (not shown) for facilitating chemical insertions intothe production formation. The communications paths facilitated by upperports 17 a and lower ports 19 a are, however, sealed off from respectiveupper and lower ports 17 and 19 as shown in FIG. 20a. When tree 2 hasbeen set, crossover stab 12 may be extended to the position shown inFIG. 20b until upper ports 17 and lower ports 19 in valve 16 align withupper ports 17 a and lower ports 19 a in tubing hanger 4, respectively.Alignment is accomplished when the shoulder 13 of shuttle valve 16contacts ledge 90 of tubing hanger 4.

[0103] Referring next to FIG. 21, the CTS is shown completely installed.The optional sequence leading up to FIG. 21 as shown includes retrievingtubing hanger plug 68 (not shown in FIG. 21), installing crossover plugs24 and 26 on wireline, retrieving BOP stack 60 (not shown in FIG. 21)and installing temporary abandonment/debris cap 42.

[0104] In view of the above disclosure, one of ordinary skill in the artshould understand and appreciate that one illustrative embodiment of thepresent invention includes a subterranean oil or gas well assembly thatincludes: a wellhead; a Christmas tree coupled to the wellhead; and atubing hanger landed within the wellhead. A sliding valve is disposedwithin the tubing hanger to selectively allow fluid communicationbetween a first port in the sliding valve and a first port in the tubinghanger. A crossover assembly is landed within the tree body, and; acrossover stab is disposed within the crossover assembly and adapted totranslate the sliding valve between open and closed positions. In apreferred version of the present illustrative embodiment, the tubinghanger is substantially concentric with the wellhead. Preferably thetubing hanger is a production tubing hanger with a production tubingsuspended therefrom. The tubing hanger can also include an annulusaccess channel extending between the first port in the tubing hanger andan annulus, the annulus being defined between the production tubing andan innermost casing. The Christmas tree preferably includes a radialannulus bore and a radial production bore. Alternatively the Christmastree includes an integral production bore valve. In one embodiment theillustrative assembly includes a plurality of annulus access channelsarranged about the tubing hanger and extending between the annulus and aplurality of first ports. Preferably the plurality of annulus accesschannels converge to a common eccentric connector. More preferably theannulus access channels reduce in number between the eccentric connectorand the Christmas tree radial annulus bore. In one particularlypreferred embodiment, the plurality of annulus access channels providesan equivalent flow area of at least 1.5 inches. The assembly of thepresent illustrative embodiment can be designed such that the crossoverstab further defines the annulus access channel. The crossover stabpreferably defines the plurality of annulus access channels.

[0105] The above described illustrative embodiment can also include a abiasing member that is disposed between the tubing hanger and thesliding valve. The biasing member biases the sliding valve to the closedposition. The crossover assembly further defines the annulus accesschannel and preferably the crossover assembly further defines more thanone annulus access channel. In one illustrative embodiment, the slidingvalve facilitates fluid communication between the annulus access channeldefined by the crossover assembly and the annulus access channel definedby the crossover stab. The illustrative embodiment of the presentinvention can alternatively include a Christmas tree that furtherdefines the annulus access channel. Preferably the crossover assemblyfurther includes a radial annulus bore and a radial production bore.More preferably, the crossover assembly further includes an orientationhelix for facilitating the alignment of the crossover radial annulusbore with the tree radial annulus bore and the crossover radialproduction bore with the tree radial production bore.

[0106] It is also contemplated that the assembly of the presentinvention includes an extendable/retractable production stab, theproduction stab being extendable between the tree radial production boreand the crossover radial production bore. In one illustrative embodimentincluding the extendable/retractable annulus stab, the annulus stab isextendable between the tree radial annulus bore and the crossover radialannulus bore. The tree and the crossover assembly are preferablyindependently retrievable when the annulus stab is retracted. In asimilar manner it is contemplated that the tree and the crossoverassembly are independently retrievable when the production stab isretracted. The production stab mechanism includes a first shaft, asecond shaft operatively connected to the first shaft by a pair of bevelgears, and a threaded connection between production stab and the firstshaft. Preferably the mechanism further includes an anti-rotation key toprevent the production stab from rotating with the first shaft. Theassembly of the present invention may also include an annulus stabmechanism in which the mechanism includes a first shaft, a second shaftoperatively connected to the first shaft by a pair of bevel gears, and athreaded connection between annulus stab and the first shaft. In onepreferred embodiment, the mechanism further includes an anti-rotationkey to prevent the annulus stab from rotating with the first shaft. Theassembly of the present illustrative embodiment alternatively includes asecond port in the sliding valve to selectively allow fluidcommunication of chemicals between the second port in the sliding valveand a second port in the tubing hanger. In such an illustrativeassembly, the tubing hanger includes a chemical injection channelextending between the second port in the tubing hanger and a productiontubing. A plurality of chemical injection channels is contemplated andmay be arranged about the tubing hanger and extending between theproduction tubing and a plurality of second ports. In one illustrativeembodiment, the plurality of chemical injection channels converge to acommon eccentric connector. Preferably the plurality of chemicalinjection channels reduce in number between the eccentric connector anda Christmas tree chemical channel and more preferably the plurality ofchemical injection channels provides an equivalent flow area of at least0.375 inches. The crossover stab, in one illustrative embodiment,further defines the chemical injection channel and it is preferred thatit defines a plurality of chemical injection channels. Alternatively thecrossover assembly can define the chemical injection channel andpreferably the crossover assembly defines the one or more chemicalinjection channels. In one illustrative embodiment, the sliding valvefacilitates fluid communication between the chemical injection channeldefined by the crossover assembly and the chemical injection channeldefined by the crossover stab. Alternatively, the Christmas tree canfurther define the chemical injection channel.

[0107] As is presently contemplated, the present invention may alsoencompass a subterranean oil or gas well assembly that includes: awellhead; a Christmas tree coupled to the wellhead; and a single boretubing hanger landed within the wellhead. The tubing hanger has aproduction tubing suspended from it The single bore tubing hangerfurther includes a plurality of first closable ports therein, the firstclosable ports facilitating fluid communication to an annulus defined bythe production tubing and an innermost casing. The single bore tubinghanger further includes a plurality of tubing hanger annulus accesschannels extending from at least one of the plurality of first closableports to the annulus. The illustrative assembly optionally includes aplurality of uphole annulus access channels in which the plurality offirst closable ports are correspondingly alignable with the upholeannulus access channels to facilitate fluid communication between theuphole annulus access channels and the tubing hanger annulus accesschannels. The illustrative assembly can alternatively include acrossover assembly landed within the tree, wherein the uphole annulusaccess channels extend through aligned radial bores in the crossoverassembly and the Christmas tree. In one such embodiment the upholeannulus access channels extend longitudinally through the Christmastree. The assembly can be embodied such that the crossover assemblyfurther includes a crossover stab and the plurality of first closableports further comprises a sliding valve. The sliding valve is operableto open and close the first closable ports to selectively allow fluidcommunication between the tubing hanger annulus access channels and theuphole annulus access channels. Alternatively, the plurality of upholeannulus access channels can converge to a common eccentric connector,such that the number of uphole annulus access channels is reducedbetween the eccentric connector and the Christmas tree. The presentillustrative assembly can be made such that the single bore tubinghanger further includes a second plurality of closable ports and aplurality of tubing hanger chemical injection channels extending fromthe second plurality of closable ports, through the tubing hanger, andto the tubing hanger bore. The assembly may alternatively be made toinclude a plurality of uphole chemical injection channels, in which theplurality of first closable ports are correspondingly alignable with theuphole chemical injection channels to facilitate fluid communicationbetween the uphole chemical injection channels and the tubing hangerchemical injection channels. The crossover assembly can be landed withinthe tree, such that the uphole chemical injection channels extendthrough aligned longitudinal bores arranged about the crossover assemblyand the Christmas tree. The crossover assembly can also include acrossover stab and the plurality of second closable ports furthercomprises a sliding valve. In such an illustrative embodiment, thesliding valve is operable to open and close the second closable ports toselectively allow fluid communication between the tubing hanger chemicalinjection channels and the uphole chemical injection channels. Inanother illustrative embodiment of the present invention, the pluralityof uphole chemical injection channels converge to a common eccentricconnector, and wherein the number of uphole chemical injection channelsis reduced between the eccentric connector and the Christmas tree.

[0108] The present invention also contemplates a method of servicing asubterranean well. Such an illustrative method includes the steps of:providing a wellhead preferably with a BOP stack mounted onto thewellhead; installing a tubing hanger the wellhead and installing achristmas tree with an internal crossover assembly mounted therein ontothe wellhead In one embodiment, the tubing hanger includes: a boreconcentric with the wellhead and a plurality of channels boredlongitudinally partially therethrough, the plurality of channels beingspaced around the circumference of the tubing hanger. In anotherembodiment, the tubing hanger further includes a plurality of firstports and a plurality of second ports and a sliding valve forselectively opening and closing the first and second pluralities ofports. In another embodiment, the Christmas tree includes anextendable/retractable stab between radial bores in the crossoverassembly and Christmas tree. The illustrative method may also includethe step of retracting the stab. Optionally, the method may include thestep of retrieving the Christmas tree separately from the tubing hanger.In another illustrative embodiment the method includes the step ofretrieving the crossover assembly and the tubing hanger while theChristmas tree remains connected to the wellhead. In yet anotherillustratvie embodiment, the method may include the step of opening thesliding valve by inserting a crossover stab to position the slidingvalve in an open position.

[0109] One of ordinary skill in the art should also appreciate that thepresent invention includes a subsea wellbore production apparatus with aside-production bore christmas tree, a production tubing hanger, and aninternal crossover assembly. It should be appreciated that theimprovement to such an apparatus includes a production stab that isretractable into the Christmas tree and extendable between radial boresin the christmas tree and the crossover assembly. In such an apparatus,the stab provides a sealed flow path between the crossover assembly andthe christmas tree. Preferably the production stab further includes anactuation mechanism. The actuation mechanism includes: a first rotatableshaft in threaded engagement with the production stab; and a rotationalkey lock preventing rotation of the production stab; such that rotationof the first shaft is translated into axial movement of the productionstab. The apparatus may also include a second rotatable shaftoperatively connected to the first rotational shaft by gears, whereinrotation of the second rotatable shaft is translated into rotation ofthe first rotational shaft. The illustrative apparatus may optionallyinclude an annulus stab which is retractable into the Christmas tree andextendable between second radial bores in the Christmas tree and thecrossover assembly. The apparatus preferably has a plurality of annulusaccess channels spaced around the tubing hanger and the crossoverassembly, and wherein the annulus access channels communicate with aChristmas tree annulus channel. In an alternative embodiment, theapparatus includes a plurality of chemical injection channels spacedaround the tubing hanger and the crossover assembly, and wherein thechemical injection channels communicate with a christmas tree chemicalinjection channel.

[0110] While the present invention has been particularly shown anddescribed with reference to a particular illustrative and preferredembodiments thereof, it will be understood by those skilled in the artthat various changes in form and details may be made without departingfrom the scope of the invention. The above-described embodiments areintended to be merely illustrative, and should not be considered aslimiting the scope of the present invention which is defined in thefollowing claims.

What is claimed is:
 1. A subterranean oil or gas well assemblycomprising: a) a wellhead; b) a christmas tree coupled to the wellhead;c) a tubing hanger landed within the wellhead; d) a sliding valvedisposed within the tubing hanger to selectively allow fluidcommunication between a first port in the sliding valve and a first portin the tubing hanger; e) a crossover assembly landed within the treebody, and; f) a crossover stab disposed within the crossover assemblyand adapted to translate the sliding valve between open and closedpositions.
 2. The assembly of claim 1 wherein the tubing hanger issubstantially concentric with the wellhead.
 3. The assembly of claim 1wherein the tubing hanger is a production tubing hanger with aproduction tubing suspended therefrom.
 4. The assembly of claim 1wherein the christmas tree further comprises a radial annulus bore and aradial production bore.
 5. The assembly of claim 4 wherein the Christmastree further comprises an integral production bore valve.
 6. Theassembly of claim 4 wherein the tubing hanger further comprises anannulus access channel extending between the first port in the tubinghanger and an annulus, the annulus being defined between the productiontubing and an innermost casing.
 7. The assembly of claim 6 furthercomprising a plurality of annulus access channels arranged about thetubing hanger and extending between the annulus and a plurality of firstports.
 8. The assembly of claim 7 wherein the plurality of annulusaccess channels converge to a common eccentric connector.
 9. Theassembly of claim 8 wherein the plurality of annulus access channelsreduce in number between the eccentric connector and the Christmas treeradial annulus bore.
 10. The assembly of claim 7 wherein the pluralityof annulus access channels provides an equivalent flow area of at least1.5 inches.
 11. The assembly of claim 6 wherein the crossover stabfurther defines the annulus access channel.
 12. The assembly of claim 7wherein the crossover stab further defines the plurality of annulusaccess channels.
 13. The assembly of claim 1 further comprising abiasing member disposed between the tubing hanger and the sliding valve.14. The assembly of claim 13 wherein the biasing member biases thesliding valve to the closed position.
 15. The assembly of claim 11wherein the crossover assembly further defines the annulus accesschannel.
 16. The assembly of claim 12 wherein the crossover assemblyfurther defines the more than one annulus access channel.
 17. Theassembly of claim 15 wherein the sliding valve facilitates fluidcommunication between the annulus access channel defined by thecrossover assembly and the annulus access channel defined by thecrossover stab.
 17. The assembly of claim 15 wherein the christmas treefurther defines the annulus access channel.
 18. The assembly of claim 4wherein the crossover assembly further comprises a radial annulus boreand a radial production bore.
 19. The assembly of claim 18 wherein thecrossover assembly further comprises an orientation helix facilitatingthe alignment of the crossover radial annulus bore with the tree radialannulus bore and the crossover radial production bore with the treeradial production bore.
 20. The assembly of claim 19 further comprisingan extendable/retractable production stab, the production stab beingextendable between the tree radial production bore and the crossoverradial production bore. 20a. The assembly of claim 20 wherein both thetree and the crossover assembly are independently retrievable when theproduction stab is retracted.
 21. The assembly of claim 20 furthercomprising an a production stab mechanism; the mechanism comprising afirst shaft, a second shaft operatively connected to the first shaft bya pair of bevel gears, and a threaded connection between production staband the first shaft.
 22. The assembly of claim 21 wherein the mechanismfurther comprises an anti-rotation key to prevent the production stabfrom rotating with the first shaft.
 23. The assembly of claim 19 furthercomprising an extendable/retractable annulus stab, the annulus stabbeing extendable between the tree radial annulus bore and the crossoverradial annulus bore. 23a. The assembly of claim 23 wherein both the treeand the crossover assembly are independently retrievable when theannulus stab is retracted.
 24. The assembly of claim 20 furthercomprising an annulus stab mechanism; the mechanism comprising a firstshaft, a second shaft operatively connected to the first shaft by a pairof bevel gears, and a threaded connection between annulus stab and thefirst shaft.
 25. The assembly of claim 21 wherein the mechanism furthercomprises an anti-rotation key to prevent the annulus stab from rotatingwith the first shaft.
 26. The assembly of claim 4 further comprising asecond port in the sliding valve to selectively allow fluidcommunication of chemicals between the second port in the sliding valveand a second port in the tubing hanger.
 27. The assembly of claim 26wherein the tubing hanger further comprises a chemical injection channelextending between the second port in the tubing hanger and a productiontubing.
 28. The assembly of claim 27 further comprising a plurality ofchemical injection channels arranged about the tubing hanger andextending between the production tubing and a plurality of second ports.29. The assembly of claim 28 wherein the plurality of chemical injectionchannels converge to a common eccentric connector.
 30. The assembly ofclaim 29 wherein the plurality of chemical injection channels reduce innumber between the eccentric connector and a Christmas tree chemicalchannel.
 31. The assembly of claim 28 wherein the plurality of chemicalinjection channels provides an equivalent flow area of at least 0.375inches.
 32. The assembly of claim 27 wherein the crossover stab furtherdefines the chemical injection channel.
 33. The assembly of claim 28wherein the crossover stab further defines the plurality of chemicalinjection channels.
 34. The assembly of claim 32 wherein the crossoverassembly further defines the chemical injection channel.
 35. Theassembly of claim 33 wherein the crossover assembly further defines theone or more chemical injection channels.
 36. The assembly of claim 34wherein the sliding valve facilitates fluid communication between thechemical injection channel defined by the crossover assembly and thechemical injection channel defined by the crossover stab.
 37. Theassembly of claim 34 wherein the Christmas tree further defines thechemical injection channel.
 38. A subterranean oil or gas well assemblycomprising: a) A wellhead; b) a christmas tree coupled to the wellhead;c) a single bore tubing hanger landed within the wellhead, the tubinghanger having a production tubing suspended therefrom; wherein thesingle bore tubing hanger further comprises a plurality of firstclosable ports therein, the first closable ports facilitating fluidcommunication to an annulus defined by the production tubing and aninnermost casing.
 39. The assembly of claim 38 wherein the single boretubing hanger further comprises a plurality of tubing hanger annulusaccess channels extending from at least one of the plurality of firstclosable ports to the annulus.
 40. The assembly of claim 39 furthercomprising a plurality of uphole annulus access channels, wherein theplurality of first closable ports are correspondingly alignable with theuphole annulus access channels to facilitate fluid communication betweenthe uphole annulus access channels and the tubing hanger annulus accesschannels.
 41. The assembly of claim 40 further comprising a crossoverassembly landed within the tree, wherein the uphole annulus accesschannels extend through aligned radial bores in the crossover assemblyand the Christmas tree. 41a. The assembly of claim 41 wherein the upholeannulus access channels extend longitudinally through the Christmastree.
 42. The assembly of claim 41 wherein the crossover assemblyfurther comprises a crossover stab and the plurality of first closableports further comprises a sliding valve.
 43. The assembly of claim 42wherein the sliding valve is operable to open and close the firstclosable ports to selectively allow fluid communication between thetubing hanger annulus access channels and the uphole annulus accesschannels.
 45. The assembly of claim 40 wherein the plurality of upholeannulus access channels converge to a common eccentric connector, andwherein the number of uphole annulus access channels is reduced betweenthe eccentric connector and the Christmas tree.
 46. The assembly ofclaim 38 wherein the single bore tubing hanger further comprises asecond plurality of closable ports and a plurality of tubing hangerchemical injection channels extending from the second plurality ofclosable ports, through the tubing hanger, and to the tubing hangerbore.
 47. The assembly of claim 46 further comprising a plurality ofuphole chemical injection channels, wherein the plurality of firstclosable ports are correspondingly alignable with the uphole chemicalinjection channels to facilitate fluid communication between the upholechemical injection channels and the tubing hanger chemical injectionchannels.
 48. The assembly of claim 47 further comprising a crossoverassembly landed within the tree, wherein the uphole chemical injectionchannels extend through aligned longitudinal bores [define] arrangedabout the crossover assembly and the Christmas tree.
 49. The assembly ofclaim 48 wherein the crossover assembly further comprises a crossoverstab and the plurality of second closable ports further comprises asliding valve.
 50. The assembly of claim 49 wherein the sliding valve isoperable to open and close the second closable ports to selectivelyallow fluid communication between the tubing hanger chemical injectionchannels and the uphole chemical injection channels.
 51. The assembly ofclaim 46 wherein the plurality of uphole chemical injection channelsconverge to a common eccentric connector, and wherein the number ofuphole chemical injection channels is reduced between the eccentricconnector and the Christmas tree.
 52. A method of servicing asubterranean well comprising the steps of: a) providing a wellhead b)installing a tubing hanger the wellhead, the tubing hanger comprising: abore concentric with the wellhead and a plurality of channels boredlongitudinally partially therethrough, the plurality of channels beingspaced around the circumference of the tubing hanger; C) installing aChristmas tree with an internal crossover assembly mounted therein ontothe wellhead; wherein the Christmas tree includes anextendable/retractable stab between radial bores in the crossoverassembly and Christmas tree.
 53. The method of claim 52 furthercomprising the step of retracting the stab.
 54. The method of claim 53further comprising the step of retrieving the Christmas tree separatelyfrom the tubing hanger.
 55. The method of claim 53 further comprisingthe step of retrieving the crossover assembly and the tubing hangerwhile the Christmas tree remains connected to the wellhead.
 56. Themethod of claim 52 wherein the tubing hanger further comprises aplurality of first ports and a plurality of second ports and a slidingvalve for selectively opening and closing the first and secondpluralities of ports.
 57. The method of claim 56 further comprising thestep of opening the sliding valve by inserting a crossover stab toposition the sliding valve in an open position.